Bestil før CONCAT_WS

Følgende burde virke, hvis værdierne er NULL og ikke tomme:

select id,
       concat_ws('||', Phone1, Phone2, Phone3)
from t

Referencen er her :

For at håndtere bestilling, ville jeg gå efter:

select id,
       group_concat(phone Separator '||' order by phone) as ConcatPhones
from (select t.id,
             (case when nums.n = 1 then phone1
                   when nums.n = 2 then phone2
                   when nums.n = 3 then phone3
              end) as phone
       from t cross join
            (select 1 as n union all select 2 union all select 3) nums
     ) p
where phone is not null
group by id

Dette vil bortfiltrere ethvert id, der ikke har et telefonnummer.

Du kan også gøre dette med en kæmpe case udtalelse, selvom det virker noget af et mareridt:

select t.id,
       (case when phone1 < phone2 and phone2 < phone3 then concat_ws('||', phone1, phone2, phone3)
             when phone1 < phone3 and phone3 < phone2 then concat_ws('||', phone1, phone3, phone2)
              . . .  through the remaining 4 permuatiations when all three are present
             when phone1 is null and phone2 < phone3 then concat_ws('||', phone2, phone3)
             . . . through the remaining 5 permutuations when one is NULL
             when phone1 is null and phone2 is null then phone3
              . . . through the remaining 2 permutations when two are NULL
        end) as ConcatPhones
from t

Dette er mere effektivt. Det er muligt for 3 telefonnumre. Jeg ønsker ikke at beskæftige mig med f.eks. fem af dem.